Clojurians Log v2

hello everyone, quick question. As I was working on the grammar definition of Clojure’s symbols and keywords for my project (parcera) I received this report about symbols being allowed to have more than one / character. Although I have seen this for keywords I didnt think it was possible for symbols. Is this a bug? or is it also “tolerated” for backwards compatibility :thinking_face: • here is the example code: https://github.com/VladimirMarkovic86/ocr-lib/blob/master/src/clj/ocr_lib/core.clj#L13 • here is the report and reproduction case: https://github.com/carocad/parcera/pull/94#issuecomment-706546263

Just a thought: clojure.core// :)

yep I am aware of that one. However in that case the namespace/simple-name still applies. The problem is something like foo/bar/baz . Which part is the namespace and which the name?

just to be clear, I am talking about a literal simbol, not one made with (symbol ns name) 😉

> '/' has special meaning, it can be used once in the middle of a symbol to separate the namespace from the name, e.g. my-namespace/foo. '/' by itself names the division function. Troll answer: whichever one is nearest the middle :D

That code in ocr-lib is nonsense

user=> (re-matches symbolPat "clojure.core//")
["clojure.core//" "clojure.core/" "/"]
user=> (re-matches symbolPat "clojure.core/foo")
["clojure.core/foo" "clojure.core/" "foo"]
user=> (re-matches symbolPat "clojure.core/foo/bar")
["clojure.core/foo/bar" "clojure.core/foo/" "bar"]
user=> 

Oh wow, I'm surprised that works…

user=> (import '[java.util Base64])
java.util.Base64
user=> (Base64/Decoder/getDecoder)
#object[java.util.Base64$Decoder 0x1237e0be "java.util.Base64$Decoder@1237e0be"]
user=> 

I actually didnt try that 😅 . Good to know. However that regex could be seen as “an implementation detail”. In parcera I dont use them anymore because the LispReader has a lot of other checks for most tokens

Hmm, annoyingly it seems that Clojure actually behaves differently in the reader and clojure.lang.Symbol.

https://github.com/clojure/clojure/blob/30a36cbe0ef936e57ddba238b7fa6d58ee1cbdce/src/jvm/clojure/lang/Symbol.java#L59-L63 boo

different behavior

I did poke around but didnt understand it. Decoder is a public static class inside Base64 class. However, Decoder doesnt have a getDecoder static method. Only Base64 has :man-shrugging::skin-tone-4:

So this should really be Base64$Decoder/getDecoder I guess?

Oh, no. I see what you mean

Is the Decoder just ignored then?

Lol, yes:

user=> (Base64/flibbetygibbit/getDecoder)
#object[java.util.Base64$Decoder 0x1d25c1c "java.util.Base64$Decoder@1d25c1c"]
user=> 

oh I didnt try that 😆

OK, figured it out I think:

user=> (Base64/flibbetygibbit/getDecoder)
sym: flibbetygibbit/getDecoder (flibbetygibbit / getDecoder)
From (flibbetygibbit/getDecoder)
Form: (. Base64 flibbetygibbit/getDecoder)
methodName: getDecoder

It's ignored by Clojure because clojure gets the name of the symbol, because it basically just wants a string

So by coincidence, it ignores the namespace in this form

It appears you can use full name java.util.Base64$Decoder to name that Java class, but there doesn't seem to be a shorter way to refer to it, no matter what import statements you use.

helpful information from alex the other day about this

@andy.fingerhut fwiw, the Decoder is completely ignored :) (Base64/foobarbaz/getDecoder) works just as well. It should be (Base64/getDecoder). It works because it expands to (. Base64 foobarbaz/getDecoder) and the Compiler uses the name of the symbol at the 3rd position.

But strangely enough, you cannot use the full name to refer to the getDecoder method in that class. Maybe I misunderstand the JVM docs for that class, though.

Doh. the getDecoder method is a method of class java.util.Base64. I think it makes more sense to me now.